McCain, the 2008 GOP presidential nominee, warned his colleagues that anyone who objected would be “carrying out the desires and ambitions of Vladimir Putin, and I do not say that lightly.”

However, Paul objected and then quickly left the chamber.

McCain said:

“I note the senator from Kentucky leaving the floor without justification or any rationale for the action that he has just taken. That is really remarkable, that a senator blocking a treaty that is supported by an overwhelming number, perhaps 98 at least, of his colleagues would come to the floor and object and walk away. And walk away!

The only conclusion you can draw when he walks away is he has no argument to be made. He has no justification for his objection to having a small nation be part of NATO that is under assault from the Russians. So, I repeat again: The senator from Kentucky is now working for Vladimir Putin.”

In 2015, McCain called Paul ― then running for the GOP presidential nomination ― “the worst possible candidate” on national security issues, and in 2013 he called him and several other Republican senators “wacko birds” for what he considered extremist views.